In the typical motor vehicle bodywork constructed from sheet metal components, it is often necessary to reinforce the sheet metal components in regions where heavy strain occurs. It is therefore common practice to employ a so-called "sheet doubling" technique whereby one or more additional metal sheets are welded onto the bodywork at the heavy strain regions. Also, the surrounding sheets are usually provided with crimps for reinforcement.
The connection of the rear safety belt anchor assembly to the vehicle floor pan is an example region in the sheet metal vehicle bodywork where large peak stresses are known to occur under load. The safety belt anchor points lie roughly in the region where the floor pan adjoins the rear longitudinal bearer member and curves upward to meet the rear seat bulkhead. In the usual practice, the above-described sheet doubling technique is employed to provide the necessary reinforcement of the single sheet floor pan at the safety belt anchor points. Additionally, the added metal sheet may include a nut cage or nut welded thereto for use in securing the anchor mechanism of the safety belt or automatic seat belt winding device. In addition to the sheet doubling, the surrounding sheets must also be crimped for further reinforcement.
The fabrication of the reinforced safety belt anchor points as described above is costly since a large number of sheet metal components are required which, in turn, requires a large number of welding and crimping steps. Aside from the localized reinforcement for the belt anchor, no other significant improvement is achieved with regard to the rigidity or vibrational behavior of the bodywork itself in the reinforced region. Further, the additional fastening of other parts of the vehicle to the added metal sheet is not possible without further modification and additional expense.
From Japanese patent document JP-A-58 136 572 there is disclosed a reinforcement arrangement for a hollow section rear pillar of a vehicle bodywork constructed of two drawn metal sheets which are welded together. The rear pillar forms a portion of the vehicle frame boundary opening for a hatch back door and is reinforced along one interior wall portion by an additional structural piece in the region where the mounting structure for the gas cylinder door opening/closing mechanism connects to the rear pillar. The reinforcing piece is shaped to correspond to the two adjacent inner walls of the hollow section rear pillar and is positively locked against these inner walls over a length thereof. A single set of screw fasteners connect both the internal reinforcing piece to the inner walls of the hollow section and the gas cylinder mounting structure to the outer walls of the hollow section. As disclosed, this is a very specific plate doubling embodiment for stiffening a hollow section bearer member as mentioned at the outset. This document does not teach or suggest a reinforcement assembly for a floor tub in the high strain region of the rear safety belt anchor points.
Reinforcing plates and reinforcing inserts in hollow section bearer members of a vehicle bodywork are also known from German patent documents DE 2 435 768 A and DE 2 412 506 A. The placement of such reinforcing plates within the hollow section bearer members is difficult and time-consuming, due to the difficult manipulation and cramped conditions in the finished state of the bodywork.
Various solutions for adjustably connecting together sheet metal components in a vehicle bodywork are known in the art. For example, Japanese patent document JP-A-1 197 182 discloses a fender bench formed as an extruded aluminum profile in which an open supporting channel is formed by two opposite claw sections which accommodate a nut plate. Furthermore, from European patent document EP 0 136 264 83 there is disclosed a known profile rod having an open supporting channel for insertion of nut plates.
However, there is still a definite need in the art for a simple and low cost solution for the reinforcement of the vehicle floor pan in the high region of the seat belt anchor point and wherein the reinforcement also includes means for easy attachment of the seat belt anchor assembly.